VIDEO HERE: http://www.youtube.com/watch?v=D7nDykz6R1o
Step one: Print one of each, but you will need two caps.
Step two: Assemble wheel onto base then cog wheel.
Step three: Press or glue pins on axles.
Step four: Spin wheel in amazement!
There are two sets of files.
The unmarked files have units in inches and the files mark "mm" at the end are in millimeters for Skienforge users.